Expression of Ki-67 and Bcl-2 biomarkers in normal breast tissue from women of reproductive age treated with raloxifene

Selective estrogen receptor modulators in the prevention of breast cancer in premenopausal women: a review

The detection of premenopausal women at high risk of breast cancer is key to chemoprevention. Therapy with selective estrogen receptor modulators (SERMs) induces a significant antiproliferative effect in estrogen receptor (ER) positive breast cancer. This review was designed according the guidelines of the 2009 PRISMA statement. Searching different databases, including PubMed, MedlinePlus, PLoS One, Cochrane Breast Cancer Specialized Register, Clinical Trials.gov and American Society of Clinical Oncology. From 168 records screened, 15 full text articles were assessed for eligibility and only 7 studies met the inclusion criteria. Three of the studies included analyzed changes in Ki-67 expression, revealing weaker expression after treatment with acolbifene and raloxifene (P<0.001). Three studies also analyzed the breast volume by magnetic resonance imagining (MRI) and demonstrate a significant difference after 1 year with raloxifene treatment (P=0.0017). Moreover, a 20% reduction in breast density was observed after a 2-year treatment with tamoxifen in premenopausal women. SERMs reduce the risk of developing breast cancer. The studies reviewed here demonstrate the modulation of Ki-67 expression and changes in breast density, suggesting an important preventive role for this group of drugs in prevention for premenopausal women at high risk of developing breast cancer.

Spatially correlated phenotyping reveals K5-positive luminal progenitor cells and p63-K5/14-positive stem cell-like cells in human breast epithelium

Understanding the mechanisms regulating human mammary epithelium requires knowledge of the cellular constituents of this tissue. Different and partially contradictory definitions and concepts describing the cellular hierarchy of mammary epithelium have been proposed, including our studies of keratins K5 and/or K14 as markers of progenitor cells. Furthermore, we and others have suggested that the p53 homolog p63 is a marker of human breast epithelial stem cells. In this investigation, we expand our previous studies by testing whether immunohistochemical staining with monospecific anti-keratin antibodies in combination with an antibody against the stem cell marker p63 might help refine the different morphologic phenotypes in normal breast epithelium. We used in situ multilabel staining for p63, different keratins, the myoepithelial marker smooth muscle actin (SMA), the estrogen receptor (ER), and Ki67 to dissect and quantify the cellular components of 16 normal pre- and postmenopausal human breast epithelial tissue samples at the single-cell level. Importantly, we confirm the existence of K5+ only cells and suggest that they, in contrast to the current view, are key luminal precursor cells from which K8/18+ progeny cells evolve. These cells are further modified by the expression of ER and Ki67. We have also identified a population of p63+K5+ cells that are only found in nipple ducts. Based on our findings, we propose a new concept of the cellular hierarchy of human breast epithelium, including K5 luminal lineage progenitors throughout the ductal-lobular axis and p63+K5+ progenitors confined to the nipple ducts.

Molecular Portrait of the Normal Human Breast Tissue and Its Influence on Breast Carcinogenesis

Normal human breast tissue consists of epithelial and nonepithelial cells with different molecular profiles and differentiation grades. This molecular heterogeneity is known to yield abnormal clones that may contribute to the development of breast carcinomas. Stem cells that are found in developing and mature breast tissue are either positive or negative for cytokeratin 19 depending on their subtype. These cells are able to generate carcinogenesis along with mature cells. However, scientific data remains controversial regarding the monoclonal or polyclonal origin of breast carcinomas. The majority of breast carcinomas originate from epithelial cells that normally express BRCA1. The consecutive loss of the BRCA1 gene leads to various abnormalities in epithelial cells. Normal breast epithelial cells also express hypoxia inducible factor (HIF) 1α and HIF-2α that are associated with a high metastatic rate and a poor prognosis for malignant lesions. The nuclear expression of estrogen receptor (ER) and progesterone receptor (PR) in normal human breast tissue is maintained in malignant tissue as well. Several controversies regarding the ability of ER and PR status to predict breast cancer outcome remain. Both ER and PR act as modulators of cell activity in normal human breast tissue. Ki-67 positivity is strongly correlated with tumor grade although its specific role in applied therapy requires further studies. Human epidermal growth factor receptor 2 (HER2) oncoprotein is less expressed in normal human breast specimens but is highly expressed in certain malignant lesions of the breast. Unlike HER2, epidermal growth factor receptor expression is similar in both normal and malignant tissues. Molecular heterogeneity is not only found in breast carcinomas but also in normal breast tissue. Therefore, the molecular mapping of normal human breast tissue might represent a key research area to fully elucidate the mechanisms of breast carcinogenesis.

Effect of tamoxifen and raloxifene on the proliferative activity of the breast epithelium in premenopausal women

OBJECTIVES

To compare the effects of tamoxifen and raloxifene on the proliferative activity of normal breast tissue in premenopausal women as measured by Ki-67/MIB-1 expression.

STUDY DESIGN

A total of 48 women with benign breast nodules and a recommendation for surgical removal of the lesion took part in this study. They were randomized to use tamoxifen or raloxifene for 22 days, after which they were submitted to surgery. During the surgical procedure, a 1-cm fragment of normal breast tissue was removed to study Ki-67 expression.

RESULTS

The mean percentage ratios between immunolabeled and non-labeled cells were 2.02 ± 1.09 and 3.13 ± 3.23 for the tamoxifen and raloxifene groups, respectively. There was no statistically significant difference between the tamoxifen (n = 16) and raloxifene (n = 14) groups in relation to the immunohistochemical analysis of Ki-67 (P = 0.205).

CONCLUSION

The results of this study showed no difference between tamoxifen and raloxifene with respect to the potential of these drugs to reduce the proliferative activity of the normal breast epithelium in premenopausal women.